.node {
  stroke-width: 1.5px;
}
.node:hover circle {
  fill: grey !important;
}

text {
  font: 14px 'Open Sans', sans-serif;
  text-anchor: middle;
  pointer-events: none;
  fill: black;
}
circle {
  fill: #ccc;
  stroke: white ;
  stroke-width: 2px;
}